1. Field of the Invention
The present invention relates to a suspension for supporting the magnetic head in a hard disk device, and more particularly to a production process for an integrated wiring type magnetic head suspension.
2. Related Art of the Invention
In conventional magnetic head suspensions used in hard disk devices, the magnetic head element is situated on one end of a springy piece of metal, with the magnetic head element and the input/output terminal of the signal processing element of the hard disk device being connected via a wire that is not integrated with the springy piece of metal.
The development of smaller, higher capacity hard disk devices in recent years has created a need for magnetic head suspensions that are per se more compact and lightweight. However, wire size and weight has not been reduced adequately relative to the springy piece of metal. If magnetic head suspensions have become more compact and lightweight, wire mass and rigidity have increased relative to the piece of springy metal, creating the problem of an inability to produce a suspension having the desired performance.
Accordingly, there has been proposed a integrated wiring type compact lightweight type magnetic head suspension in which the desired performance is achieved by integrating lightweight wiring with the piece of springy metal (Japanese Patent Application Laid-open No. HEI9-306114). The wiring for this integrated wiring type magnetic head suspension is produced in the manner illustrated in FIGS. 3A to 3G.
First, a laminate material of stainless steel foil (springy piece) 31/polyimide film (insulating base) 32/copper foil (wiring) 33 laminated using an adhesive (not shown) is prepared (FIG. 3A).
The copper foil 33 in the laminate material is patterned by a photolithographic process to form a metal mask 34 (FIG. 3B). This metal mask 34 functions as an etching mask for etching the polyimide film 32 to give an insulating base 35 of the desired configuration (see FIG. 3C). Examples of the etching method used here include irradiation with excimer laser light, plasma etching, strong alkali wet etching, etc.
Next, the laminate material is irradiated from the metal mask 34 side with, e.g., excimer laser light L, and the polyimide film 32 in the exposed areas is removed by photoetching (leaving sufficient thickness to prevent the stainless steel foil 31 from being exposed) to form the insulating base 35 (FIG. 3C).
Next, the metal mask 34 is patterned by a photolithographic technique to form a line 36 (FIG. 3D).
Next, the thin polyimide film over the stainless steel foil 31, except for the insulating base 35, is removed through photoetching by irradiation with the excimer laser light L (FIG. 3E).
Next, a cover coat layer 37 is formed over the lines 36 using ordinary methods (FIG. 3F). This process gives an integrated wiring type magnetic head suspension. Optionally, the stainless steel foil 31 is typically subjected to a bending process to improve the mechanical properties of the suspension (FIG. 3G).
However, the production process for the integrated wiring type magnetic head suspension depicted in FIGS. 3A to 3G requires that the copper foil are patterned twice (for the metal mask patterning and the line patterning), and there is a search for unification of the copper foil patterning process. Regarding methods for patterning the polyimide film which serves as the insulating base, irradiation with excimer laser light involves high equipment costs, frequent maintenance, high running costs, deposition of conductive carbonized material on the laser irradiated area, and other problems. Wet etching methods require the use of expensive etchants which are also harmful to humans, and thus pose a number of problems in terms of operating safety and disposal.
The present invention is intended to solve the drawbacks of the technology described above, and its object is to provide a production process for an integrated wiring type magnetic head suspension whereby the copper foil for the lines can be patterned in a single process, and the insulating base can be produced simply and inexpensively.
The inventors perfected the present invention on the basis of the discovery that a polyimide precursor layer (e.g., a polyamic acid layer, etc.), being thermoplastic, exhibits excellent adhesion, and can be readily removed through a process of salt formation with inexpensive alkalis followed by treatment warm water; that the precursor layer can be converted into a polyimide exhibiting excellent adhesion, heat resistance, and dimensional stability by means of an imidation process that does not require equipment costs and may be carried out by a simple procedure; and that the polyimide precursor layer can withstand the conditions for copper foil patterning (acid etchants, etc.), obviating the need for the copper foil to function as a metal mask so that copper foil patterning can be accomplished in a single step.
Specifically, the present invention provides a process for producing a magnetic head suspension, comprising steps of:
(a) forming a polyimide precursor layer over a springy material layer;
(b) forming a metal layer for lines over the polyimide precursor layer;
(c) patterning the metal layer by the subtractive process to produce the lines;
(d) patterning the polyimide precursor layer by a photolithographic technique so as to give a configuration corresponding to the polyimide insulating base layer;
(e) imidating the patterned polyimide precursor layer to produce the polyimide insulating base layer; and
(f) forming a cover coat layer over the lines.
In this process, step (f) may be performed after step (e); alternatively, step (f) may comprise:
an initial step coming between step (c) and step (d), wherein a cover coat polyimide precursor layer is provided over the lines;
an intermediate step wherein this cover coat polyimide precursor layer is patterned to the desired cover coat layer configuration simultaneously with patterning of the polyimide precursor layer to the configuration corresponding to the polyimide insulating base layer in step (d); and
a final step wherein the cover coat polyimide precursor layer is imidated to form the cover coat layer simultaneously with formation of the polyimide insulating base layer in step (e).
In another aspect, the present invention provides a process for producing a magnetic head suspension, comprising steps of:
(aa) forming a polyimide precursor layer over a springy material layer;
(bb) forming lines on the polyimide precursor layer by the semiadditive process;
(cc) patterning the polyimide precursor layer by a photolithographic technique so as to give a configuration corresponding to the polyimide insulating base layer;
(dd) imidating the patterned polyimide precursor layer to produce the polyimide insulating base layer; and
(ee) forming a cover coat layer over the lines.
In this process, step (ee) may be performed after step (dd); alternatively step (ee) may comprise:
an initial step coming between step (bb) and step (cc), wherein a cover coat polyimide precursor layer is provided over the lines;
an intermediate step wherein this cover coat polyimide precursor layer is patterned to the desired cover coat layer configuration simultaneously with patterning of the polyimide precursor layer to the configuration corresponding to the polyimide insulating base layer in step (cc); and
a final step wherein the cover coat polyimide precursor layer is imidated to form the cover coat layer simultaneously with formation of the polyimide insulating base layer in step (dd).
These and other objects, features and advantages of the present invention are described in or will become apparent from the following detailed description of the invention.